Study On Triaxial Rheological Mechanical Behavior And Damage Evolution Mechanism Of Diorite Porphyrite

In the process of underground space development and exploration,permanent structures such as tunnels(alleys)and chambers will produce creep characteristics and even creep failure in high stress environment,which always threatens the safety and stability of underground space structures.Therefore,comprehensive and in-depth understanding of rock creep mechanical characteristics and revealing its failure mechanism are of great significance for maintaining the stability of the surrounding rock of underground space structure and ensuring the safe and efficient mining of underground resources.Based on this,with the engineering background of the underground powerhouse of Jurong Hydropower Station in Jiangsu province,this thesis studied the instantaneous mechanics and creep mechanics characteristics of diorite porphyry in the surrounding rock of the underground powerhouse of the hydropower station by combining laboratory tests,theoretical research and numerical simulation,established a creep damage constitutive model considering aging damage,and simulated the rock deformation and failure process.The crack development characteristics in the creep process of rock were determined,and the creep failure mechanism of diorite porphyrite was further revealed.The main research contents of this thesis are as follows:(1)Conventional triaxial compression tests,creep tests under fractional loading and cyclic loading were carried out to study the instantaneous mechanical behavior of diorite porphyrite under different confining pressures and the creep mechanical behavior of diorite porphyrite under different loading methods,and the influence law of creep stress on deformation parameters,aging deformation and strain rate in the creep process was obtained.The influence of creep loading mode on deformation characteristics,long-term strength and fracture mode of diorite porphyrite was analyzed.(2)Based on the strain separation results of cyclic loading and unloading creep tests,the damage creep model of diorite porphyrite at the accelerated creep stage under cyclic loading and unloading creep tests was established by considering the characteristics of instantaneous elasticity,instantaneous plasticity,viscoelastic and viscoplastic deformation and combining with the time-dependent damage theory.The model curve was compared with the creep test curve under stepwise loading,and the coincidence was high,which verifies the applicability of the model.(3)Based on the parallel bonding model in PFC3 D and modified by FISH language,the stress corrosion model was constructed.The effects of confining pressure on the strength and deformation of diorite porphyrite during conventional triaxial compression were simulated by stress corrosion model,and the process of microcrack germination,propagation and penetration was revealed from the microscopic perspective.At the same time,the stress corrosion model can better reflect the accelerated creep stage of the creep process,and reveal the microcrack evolution law in the creep simulation process of stepwise loading and cyclic loading.There are 74 figures,14 tables and 123 references in the dissertation.